N5 Chemistry MC 2018

Which of the following changes would not speed up a chemical reaction?

• Increasing the particle size

• Increasing the temperature

• Increasing the concentration

• Addition of a catalyst

Answer explanation

Increasing the particle size decreases the surface area, and will therefore slow down a chemical reaction.

Which line in the table identifies the correct location of a proton and an electron in an atom?

• A

• B

• C

• D

Answer explanation

Which of the following elements does not exist as diatomic molecules?

• Oxygen

• Helium

• Bromine

• Hydrogen

Answer explanation

Helium is a (monatomic) noble gas

The shapes of some molecules are shown below. The shape of a molecule of hydrogen bromide is likely to be

• tetrahedral

• trigonal pyramidal

• angular

• linear

Answer explanation

Hydrogen bromide has the formula HBr using the cross-over rule.

The correct structure for this can only be linear.

Which of the following elements forms an ion with a single positive charge and an electron arrangement of 2,8?

You may wish to use the data booklet to help you.

• Sodium

• Magnesium

• Fluorine

• Neon

Answer explanation

A Na atoms have electron arrangement 2,8,1 - Na⁺ ions have arrangement 2,8

B Mg atoms have electron arrangement 2,8,2 - Mg⁺ ions have arrangement 2,8,1

C F atoms have electron arrangement 2,7 - F⁺ ions have arrangement 2,6

D Ne atoms have electron arrangement 2,8 - Na⁺ ions have arrangement 2,7

Which line in the table shows the properties of a covalent network compound?

• A

• B

• C

• D

Answer explanation

A Bonding type is covalent molecular as it does not conduct and has low mpt/bpt

B Bonding type is ionic as is does not conduct as solid but does conduct as liquid

C Bonding type is metallic as it conducts both as a solid and a liquid

D Bonding type is covalent network as it does no conduct and has very high mpt

0·1 mol of sodium hydroxide was dissolved in water and the solution made up to 250 cm³.

What is the concentration, in mol l^-1, of the sodium hydroxide solution?

• 0·0004

• 0·025

• 0·4

• 2·5

Answer explanation

An alkaline solution contains

• only hydroxide ions

• more hydroxide ions than hydrogen ions

• more hydrogen ions than hydroxide ions

• equal numbers of hydrogen ions and hydroxide ions

Answer explanation

A An alkaline solution contains more OH^- ions than H⁺ ions (still contains some H⁺)

B An alkaline solution contains more OH^- ions than H⁺ ions

C An acidic solution contains more H⁺ ions than OH^- ions

D A neutral solution contains equal numbers of H⁺ ions and OH^- ions

A student made some statements about the effect of adding water to an acidic solution.

Identify the correct statement.

• The pH of the solution will remain the same.

• The pH of the solution will decrease.

• The hydrogen ion concentration will decrease.

• The hydrogen ion concentration will increase.

Answer explanation

A Diluting acids with water increases pH until it reaches pH=7

B Diluting acids with water increases pH until it reaches pH=7

C Diluting acids with water decreases the H+ ion concentration as water is added

D Diluting acids with water decreases the H+ ion concentration as water is added

The shortened structural formula for a compound is

CH₃CH₂CH(CH₃)CH(CH₃)CH₂CH₂CH₃

Which of the following is another way of representing this structure?

• 
• 
• 
• 

Answer explanation

C₉H₂₀ structure drawn is the isomer 3,4-dimethylheptane

A C₉H₂₀ structure is 2,4-dimethylheptane - different isomer not same structure

B C₈H₁₈ structure is 3,4-dimethylhexane - different formula not same structure

C C₉H₂₀ structure is 3,3-dimethylheptane - different isomer not same structure

D C₉H₂₀ structure is 3,4-dimethylheptane - same formula and same structure